Seal devices have been used in a variety of applications to prevent fluid from leaking between joined pieces. For example, a seal device is interposed and compressed between flanged end-connections of a flow line where in-line process control equipment is installed. In-line process control equipment includes valves, pumps, flow meters, temperature and pressure controllers and the like. This equipment usually cannot be welded into the flow line because time-scheduled maintenance requires temporary removal of this equipment and, occasionally, depleted equipment must be removed for replacement. In-line process control equipment is used in a variety of industries such as the chemical industry for processing, transporting and dispensing a myriad of chemicals and chemical compounds as well as the oil and gas industry for recovering, distributing and processing oil, gas and by-products thereof.
There are several reasons why the efficacy of a seal device is important to the user. First, failure of the seal device could cause significant environmental damage. Second, a high capital investment is typically associated with transporting fluids through a flow line system and leakage of the fluid must be prevented to protect this expensive system from potential damage. Third, a high labor cost is often associated with repair of a damaged flow line system. Numerous problems cause seal devices to leak. Such problems include corrosion, over-torqueing, under-torqueing, temperature, pressure and velocity of the fluid, to name a few.
Most any fluid can be considered corrosive. For example, even water might be considered slightly corrosive if its pH deviates from 7.0; hydrochloric acid having a low pH and hydrogen peroxide having a high pH might be considered highly corrosive. Occasionally, the material used to fabricate the seal device is not compatible with the corrosive nature of the fluid contained in the flow line. Corrosion causes the seal device to deteriorate and, unless it is timely replaced, fluid leakage or subsequent seal blow-out can occur. Also, the temperature and pressure of the corrosive fluid could accelerate the rate by which the seal device deteriorates. Sometimes a single flow line is used to transport two or more types of fluids at different times. The material used to fabricate the seal device might be compatible with one type of fluid but not the other. Thus, one fluid could cause the seal device to corrode and, subsequently, it could fail.
To compress the seal device between the flanged end-connections of the joined pieces in the flow line, fasteners, such as a common nut and bolt combination, are often used. Although installation instructions of a particular seal device might include specific torque requirements for proper sealing, an installer still might apply too much torque or too little torque. It is also possible that even if the correct range of torque is applied to the fasteners, the amount of compression force is distributed unevenly around the seal device. When compressed, the seal device then may not deform in a uniform manner. Thus, improper torqueing of the fasteners to compress the seal device may result in leakage of the fluid from the flow line.
Particularly in industrial applications, a seal device is not recommended for re-use after it has been removed from operations. This is due to the fact that the material used to fabricate the seal device deforms when it is compressed between the joined pieces in a flow line. The material deforms within its modulus of elasticity during operations but does not recover fully thereafter. If this used seal device is placed back into operation, it is possible that further compression of it will extend beyond its modulus of elasticity thus destroying its sealing capabilities.
Furthermore, during operations, the seal device is acted upon by the hydrodynamic and hydrostatic forces exerted by the fluid. Generally, such forces act on commonly known seal devices in a manner that cause the seal device to expand radially outwardly, that is, in the plane of the flanges. Little, if any, of these forces is directed towards improving the sealing characteristics of the seal device.
It is possible in some applications that the temperature and/or the pressure of the fluid might fluctuate throughout a range. Temperature and/or pressure fluctuations can cause thermal and mechanical expansion and contraction of the material comprising the seal device. Unless the material chosen for fabrication of the seal device has been selected with these design considerations in mind, it is possible that the sealing device could lose its sealing capabilities due to material fatigue caused by numerous cycles of thermal and mechanical expansion and contraction.
Given the problems in seal devices as stated above, a need exists to improve seal technology. It would be advantageous if an improved seal device could be designed for improved sealing capability by utilizing the hydrodynamic and hydrostatic forces of the fluid contained in the flow line. It would also be advantageous if the sealing device could be fabricated from corrosion resistant materials which could resist corrosion in a highly corrosive environment. Another need in the current seal technology would be to provide a seal device that is less sensitive to exacting torqueing requirements so that there is no effect upon the performance of the seal device as a result thereof. Another need would be to provide a seal device that can be reused even though it has been used in prior operations.
Another need would be to provide an improved seal device that would be generally insensitive to expansion and contraction cycles due to fluctuations in temperature and/or pressure. Another need would be to produce a seal device which would be compatible with a variety of fluids regardless of their corrosive nature, temperature and/or pressure. The present invention is directed to such an improved seal device.